Stack type recuperator having a liquid seal

ABSTRACT

This invention relates to a metallic recuperator having a liquid seal. The liquid seal utilizes a thermal barrier and allows thermal expansion and contraction of the metallic heat exchange surface, while permitting free movement thereof.

United States. Patent [191 Beggs STACK TYPE RECUPERATOR HAVING A LIQUIDSEAL [75] Inventor: Donald Beggs, Toledo, Ohio [73] Assignee: MildrexCorporation, Toledo. Ohio [221 Filed: Apr. 16, 1970 [21] App]. No:29,080

[52] US. Cl 165/32, 165/142, 165/134 [51 1 Int. Cl. R05d 23/00 [58]Field of Search 165/32, 154, 142, 169, 165/134 [56] References CitedUNITED STATES PATENTS 2,332.450 10/1943 Mantle 165/142 This inventionrelates to a metallic recuperator having a liquid seal. The liquid sealutilizes a thermal barrier June 4, 1974 3.346.042 10/1967 Seehausen..165/154 Primary E.\uminer-Charles Sukalo Attorney. Agent. or FirmPeterVrahotes; Henry Kozak ABSTRACT and allows thermal expansion andcontraction of the metallic heat exchange surface, while permitting freemovement thereof.

7 Claims, 3 Drawing Figures sum 2 or 2 PATENIEDJun 4:914

INVENTOR. flow/41 0 5666s 1 STACK TYPE RECUPERATOR HAVING A LIQUID SEALIn the fuel fired industrial furnace field, heat exchangers are commonlyemployed to preheat combustion air by extracting heat from hotcombustion gases leaving a furnace. One common type of such heatexchanger is the stack type recuperator, which is a type particularlyadapted to large size industrial furnaces such as steel mill soakingpits and slab heating furnaces. A stack type recuperator generallyconsists of a self supporting, vertically oriented, cylindrically shapedsteel outer shell which is lined internally with refractory. Acylindrically shaped, heat resisting liner is positioned within therefractory lining to form an annulus therebetween. I-Iot exhaust gasesare admitted to the lower region of the alloy liner and flow upwardlyand are discharged from the top. Air to be heated passes through theannulus betweenthe liner and the refractory lining, normally incounterflow relationship to the hot gases. The alloy liner is generallyfixed to the outer steel shell at the top; means is provided to allowthermal expansion at its lower end. The commonly employed means toaccommodate vertical movement of the lower end of the liner, and alsoprovide a pressure seal between the combustion air and hot gases, is alarge stainless steel bellows. Such bellows are not only costly, but areoften a continual source of maintenance due to the occurrence of leaks.In addition, the bellows often tend to impose strains on alloy liners asthey expand and contract, which strains tend to buckle and shorten theuseful life of such liners. It has been found that the bellows may bereplaced with a liquid seal which accommodates the need of thermalexpansion without the shortcomings associated with the bellows.

OB] ECTS DRAWING In the drawing,

FIG. 1 shows a generally elevational view, in section, of a stack typemetallic recuperator incorporating the seal of the present invention.

FIG. 2 shows the seal arrangement of FIG. 1 in greater detail.

FIG. 3 shows another embodiment of the seal for a stack recuperator.

DETAILED DESCRIPTION Referring to the drawing in FIG. 1, a stack typemetallic recuperator is shown generally at 10 including a housing 12having a cylindrical steel shell 11 and a supporting base 13. Thehousing 12 is lined with a refractory 15, such as insulating firebrickwhich will resist wind abrasion. A generally cylindrical heat resistingmetallic or alloy sleeve 17 depends from the upper end of the housing 12by a conical section 19 which is secured in an airtight manner to theshell 11, such as by welding to a flange region 21. The alloy sleeve 17is spaced apart from the refractory lining 15 by suitable spacerbrackets 23 fastened to the steel shell 11, thereby forming an annularair passage 25. Located at the upper end of the shell 11 is an opening26 which receives a pipe 27 through which cold air to be preheated isintroduced into a plenum 29 which is defined by the conical section 19,the shell 15, and the top surface of the refractory 15. Located at thelower portion of the refractory lining 15 is an annular air plenum 31having an opening 32 that receives an air pipe 33. The air pipe 33generally leads to a furnace burner or burners (not shown). Locatedbelow the air plenum 31 is a hot gas pipe 35. A refractory lined innerwall member 37 is located in the lower end of the housing 12. The wallmember 37 has an annular wall 34, which extends into the sleeve 17, abase 36, and an opening 38 which provides communication between the pipe35 and the central portion of the recuperator 10. The wall member 37 issecuredat its upper region by a heat resisting alloy cylinder 39 havingfastened thereto a base ring 41 which contacts the outer shell 11, thecombination thereof forming an annular well or vessel 43. The annularwell 43 is adapted to contain a liquid, such as water, and receives thelower portion of the alloy sleeve 17 to define a section on each side ofthe sleeve portion received therein. The well 43 has an opening 44 whichis in communication with a reservoir tank 45 by means of a pipe 47extending therebetween.

Referring now to FIG. 2, the reservoir tank 45 has a weir 49 locatedtherein to control the level of liquid. A feed line 51 is located abovethe reservoir tank 45 supplying liquid thereto, and a drain 53 islocated adjacent the weir 49 to drain the surplus liquid. The waterlevel in reservoir tank 45 is indicated at 55 and the water level inwell 43 is indicated by 57 on the inner side of the sleeve 17 and by 59and 60 on the opposite side of the sleeve 17.

In FIG. 3, an alternate arrangement is shown for maintaining asubstantially constant level of water in the well 43 on the inner sideof liner 17. Water is supplied by a pipe 63 having a valve 64. Astandpipe 57 positioned on the inside of liner 17 serves as a weir toremove fluid overflow in the well through pipe 65 which leads to a drain67.

DESCRIPTION OF OPERATION Cold air to be preheated is introduced throughpipe 27 into the plenum 29 from which the air flows down wardly throughannulus 25 to a preheated air plenum 31 and out preheated air pipe 33,as shown generally by the flow arrows. The air pipe 33 suppliespreheated air to furnace burners which generate the hot gases used toheat work or supply heat for a process, the spent gases of which areused by the recuperator 10 to preheat air. The hot spent gases areintroduced into the base region through the pipe 35 and flow into therefractory lined inner wall member 37, and thence flow upwardly insidethe alloy sleeve 17 and exit at the top of the recuperator 10. As thesleeve 17 is made'of a metal or alloy, an exchange of thermal energywill take place between the air flowing through plenum 25 and the spentgases flowing within the sleeve 17.

the flow of hot spent gasesis low or high, since the sleeve 17 is opento the atmosphere at the top end. The static pressure of the preheatedair external of the sleeve 17 will normally-be a positive pressure dueto the back pressure imposed on the combustion air system by theburners, and this pressure will vary as the flow of air may vary. Whenthe preheated air back pressure is 0, the water level would be in theposition as indicated at 57 and 59 and both will be substantially thesame as water level 55 in tank 45. As the preheated air back pressureincreases above 0, water level 59 depresses as indicated at 60,but'water level 57 and 55 remains substantially the same due toequalizing pipe 47. In this manner, compensation is made for thedifferential in pressure between the inside of liner 17 and within theair plenum 25. It is evident that the liquid 43 should not beoverheated; otherwise it would boil, thereby affecting its utility aswll asadding vapor to the preheated air conveyed by pipe 33. The innerwall 37, which extends appreciably above the water level 57 in the well43, serves as a thermal barrier wall to prevent the liner 17 from directexposure to radiation and hot gases in the region immediately above theliquid seal. The elevation of vimmersion of the lower end of liner 17into the liquid remains substantially constant. These features, whichserve to eliminate sharp thermal gradients and severe quenching effectson the liner 17, together with the complete freedom of vertical movementof the liner, are believed to be a significant improvement in the art ofsealing recuperators of the general type described.

lclaim:

l. A metallic stack type recuperator, comprising: a generally verticalhousing closed at its lower end and open at its'upper'end, a metallicsleeve received within said housing and defining a plenum therebetween,means for closingsaid plenum at the top thereof, wall means forming avessel located at the bottom of said housing and receiving the bottomportion of said sleeve, a liquid contained within said vessel, a bottomportion of said sleeve being immersed in said liquid,

interigrgf said wall member.

, '4 means for supplying a first fluid at the upper portion of saidplenum, means for removing said first fluid from the lower portion ofsaid plenum, and means for supplying a second fluid to the interior ofsaid sleeve.

2. The metallic recuperator of claim 1, including means for regulatingthe level of said liquid in said vessel.

3. The metallic recuperator of claim 1 ,including wall means locatedabove said liquid level to shield said liquid from exposureto theinterior of said recuperator.

4. The metallic recuperator of claim 1 wherein the inside wall of saidvessel extends for a distance parallel to said sleeve, thereby thermallyshielding a portion of said sleeve.

5. A metallic stack type recuperator, comprising: a generallycylindrical housing closed at its lower end and having a refractoryinterior lining, a cylindrical metallic sleeve received within the upperportion of said housing anddefining a plenum therebetween, means forclosing said plenum at the top thereof, a cylindrical wall member seatedat the bottom of said housing and extending within the bottom portion ofsaid sleeve, a base ring located below said sleeve and extending fromsaid wall member to said housing to define in cooperation with said wallmember, said housing, and said sleeve a two sectioned vessel having. thefirst section in communication with said plenum and the second sectionin communication with the interior of said'sleeve and confluent withsaid first section, a liquid contained within saidvessel, a bottomportion of said sleeve being immersed'in said liquid, means forsupplying a first fluid at the upper portion of said plenum, means forremoving said first fluid from the lower portion of said plenum, andmeans for supplying a second fluid to the b? The Eiaiiic"'rtibior ofclaim 1, including means for regulating the level of said liquid in saidvessel.

7. The recuperator of claim 5 wherein the top of said cylindrical wallmember is substantially in horizontal alignment with said means forremoving said first fluid.

1. A metallic stack type recuperator, comprising: a generally verticalhousing closed at its lower end and open at its upper end, a metallicsleeve received within said housing and defining a plenum therebetween,means for closing said plenum at the top thereof, wall means forming avessel located at the bottom of said housing and receiving the bottomportion of said sleeve, a liquid contained within said vessel, a bottomportion of said sleeve being immersed in said liquid, means forsupplying a first fluid at the upper portion of said plenum, means forremoving said first fluid from the lower portion of said plenum, andmeans for supplying a second fluid to the interior of said sleeve. 2.The metallic recuperator of claim 1, including means for regulating thelevel of said liquid in said vessel.
 3. The metallic recuperator ofclaim 1, including wall means located above said liquid level to shieldsaid liquid from exposure to the interior of said recuperator.
 4. Themetallic recuperator of claim 1 wherein the inside wall of said vesselextends for a distance parallel to said sleeve, thereby thermallyshielding a portion of said sleeve.
 5. A metallic stack typerecuperator, comprising: a generally cylindrical housing closed at itslower end and having a refractory interior lining, a cylindricalmetallic sleeve received within the upper portion of said housing anddefining a plenum therebetween, means for closing said plenum at the topthereof, a cylindrical wall member seated at the bottom of said housingand extending within the bottom portion of said sleeve, a base ringlocated below said sleeve and extending from said wall member to saidhousing to define in cooperation with said wall member, said housing,and said sleeve a two sectioned vessel having the first section incommunication with said plenum and the second section in communicationwith the interior of said sleeve and confluent with said first section,a liquid contained within said vessel, a bottom portion of said sleevebeing immersed in said liquid, means for supplying a first fluid at theupper portion of said plenum, means for removing said first fluid fromthe lower portion of said plenum, and means for supplying a second fluidto the interior of said wall means.
 6. The metallic recuperator of claim1, including means for regulating the level of said liquid in saidvessel.
 7. The recuperator of claim 5 wherein the top of saidcylindrical wall member is substantially in horizontal alignment withsaid means for removing said first fluid.